In a system in which a waveguide cable transmits high-frequency signals, e.g., millimeter-wave signals or microwave signals, it is necessary to connect a feeder wire on a circuit board and a waveguide cable. In the past, this connection is established by using a waveguide-microstrip line converter, which includes a short stub of ¼ wavelength (approximately) made of antipodal lines and short-circuited on a tube wall of the waveguide (for example, see Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-open No. H04-271501